Method of sizing paper



Patent ed Aug 1, 1944' mn'rnop or srzinc PAPER Robert S. mm, Rochester, N. y., designer to Eastman Kodak Company, Boob ester, N. Y., a

corporation of New Jersey No Drawing. Application July 10, 1941,

; Serial No. 402.119

6 Claim. (CL 117-156) This invention relates to a method of, sizing paper'with gelatin and a dihydroxymethyl urea.

In the manufacture of paper it is oftentimes desirable to pass the paper through a'solutlon of animal glue or gelatin to increase certain of the physical characteristics of the paper, such as water resistance, wet strength and smoothness.

.to give the desired results (ordinarily within the range: of '0.5-5% and preferably not more than Often, at the present time, this gelatin is-hardened by passing the paper sheet, after treatment with the gelatin, through a solution of formaldehyde and/or chromium salts, or by fuming the,

paper with formaldehyde. Fuming of the paper,

sized with gelatin, with formaldehyde'results in decidedly higher wet strength and greater blister resistance than hardening of gelatin size. by passing it through a water solution of formaldehyde. This fuming operation, however, necessitates an extra step in the manufacturing process and the use of additional equipment.

An object of this invention is to provide a method of sizing paper, having a wet strength and blister resistance, comparable, to that of gelatin-sized paper which has been treated. with formaldehyde gas but withoutthenecessity ofan extra step in the process and additional equipment in carrying it out. Another object of this invention is to provide a method of fuming the gelatin size of a paper sheet with formaldehyde from within the sheet during the processing operation. Other objects of my invention will appear herein.

I have'foun'd that by incorporating one of the class of dihydroxymethyl ureas, such as dihydroxymethyl urea, dihydrcxymethyl thiourea and 3%) as too great an amount of resin in the paper will make for brittleness. In'cases where brittleness is not objectionable or is even desirable,

larger proportions of a dihydroxymethyl urea may be employed. r

Formaldehyde is liberated from a dihydroxymethyl'urea by the action of heat. Heat is ordi-' narily applied to a paper sheet when it is'passed over hot drying drums and use may be made of this heat in liberating formaldehyde from the di-hydroxymethyl urea in the sizing composition of this invention. The gelatin is hardened in this operation by the liberated formaldehyde. Asa

.- heat operation is necessary to liberate formaldetemperatures ordinarily employed for the hot drying drums in paper manufacture such as 220- cellulose of. the paper sheet, may be. employed.

The literature states that dihydroxymethyl urea loses water and formaldehyde when subjected to a temperature above its condensation point. The

240 F. may be employed with entire satisfaction in this process.

dihydroxymethyl guanidine in a gelatin sizing 3 solution for paper that the gelatin size is hardened within the paper upon the application of heat, such as in the drying operation making. the paper. I have found that the resulting paper paper sheetwith formaldehyde fumes without a 48 I .fuming box. Obviously the gelatin and the divhydroxymethyl'urea may be applied to the paper from separate solutions prior to the heat treatment.

The dihydroxymethyl ureas exert a hardening. M eflect upon gelatin sizing if used in any amount up to the limit of solubilityin the sizing composi- -tion. As, however, there is a. tendency for this type of compound to. iorm resins, it is preferred has a much higher wet strength and greater ,49

Ifthe ordinary drying of the paper does not give a pape'rof the desired wet strength, the time of treatment may be lengthened such as bypassing the paper'over the rolls more slowly or. a

In hardening gelatin, in accordance withthis invention,- the use of the technical grade of dihydroxymethyl urea is ordinarily satisfactory.

For instance, in the case of dimethylol urea, thev commercial grade may be employed even though there may also be present therein monomethylol urea and some polymeric material as well as small amounts of formaldehyde and urea. Dimethylol.

urea slowly transforms itself from the monomeric to the polymeric form upon standing at normal temperatures so that even if the material initial- 1y on hand is 100% monomena measurable quantity of polymer-will be present if the dimethylol urea has been standing for a. short time before that only suflieient dihydroxymethyl urea be used so 'Ihls condensation proceeds upon standing 2 g v assess:

rolls tal, remove excess size and immediately passedoverhotdryingdrumswherethepaper atsucharate thatafterafewmonthsthedimethylol urea is no longer water soluble and hence cannot be used. The presence of polymeric dimethylolurea does not interfere with the hardening action of the/monomeric compound providing 5 there is not enough of the polymer present to render the dimethylol urea, incapable of being dispersed in water.

- The dihydrozymethyl ureas aenerally'are sultherein. If the paper is to be used for some specine purpose. it may be that'one particulardihydroxymethyl urea will be found'to bemore suitable than others. Flor instance. for, paper upon I which a photogr phi em ion is to be M. 'i'5',l'arly good for this purpose. For instance, an' amount of aluminum sulfate of approximately. 0.03% works 'uuite satisfactory in this connection. It in the above-given sizing composition a I have found that dimethylol urea isparticularly suitable due to its completeinertuess thereto. If desired. a mixture of these hardeninl filents may be employed in the sizing solution or other mateis dried and formaldehyde is liberated from the dimethylol urea. A paper having a good blister resistance and wet strength was obtained;

Sometimes to speed up or catalyze the decom- "position of the dihydroxymethyl urea, it is deable for use in hardenint' gel tin escri e 10 quantities of acid or acidic salt greater than 1%, such as up to 3% may be eflective, it is preferred to use a -quantity of decomposition catalyst less than'1% in the-eaeess bath. The water-soluble saltsofweakbasesandstrongacidsarepartlcuf small proportion of aluminum sulfate is incurrials, such as hexamethylene tetramine. may also so porated, the decomposition of the dimethylol-urea be incorporated in the sizing solution along with the usual proportionsof gelatin used will be withinthe'range of 2% to 10% because when more .than 10% of "gelatin is used the sizing compositionisordinarily too unless alow viscostherein is accelerated when the paper containing it is passed over drying-drums. Some catalysts which may be employed instead of aluminum sulfateare ammonium chloride, zinc chloride. sillmay be varied as desired, as a practicalmatter gs furlc acid, "hydrochloric acid, sodium bisulfate,

phosphoric acid and acetic acid. The reaction in invention proceeds at a good rate under -mildly acid conditions and any compound which will lower the pH of the sizing composition and ity gelatin is employed and a proportion of gela-v so which is compatible with the conditions of opertin less than. 2% does not have. a sufliciently pronounced sizing effect for most purposes. A sizing composition of gelatin and water 'containing a dihydroxymethyl urea is suitable for ation will serve as a catalyst in this invention.

I have found that the wet-strength imparting properties of a mixture of gelatin and. a dim- ,droxymethyl 'urea accompanied by heat treatsizing both papers made from wood fiber and as inent ismuch'greater than "would be expected those made from rag iiber as well as papers made using a mixture ofthose iibe and chromium salts. After;drying'tlie paper by passing over hotdryingdrums. thewet strength was found to be 1'! as compared to 9 for paper sized in same 'mannerfexcept that the di- '45, strengthoflO swas'obtained. hsampleofthis' .atin and l%' dimethylol urea in'additlon to form,-

aldehyde salts. .The paper, which was dried by over the hot 11. 7 18 drums, showed a wet strength of 40 as comparedto"l6% for similar papersised'in manne -with" gelatin hardened with formaldehyde butin which -56 thesdimethylolurea was omitted. in a third case using 10.0%- rag fiber and but 3% dimethylol urea,

the other-conditions being the same. as before.

apaper, having'a wetstrengt'h of 47, was obl .-'as'compared to 16% tor-the paper sisedz'd 'sistance is adaptedfparticularly tou ses involv ing immersion such as for photographic or photostatic purposes in which the products are mentinblisterresistancewasnotedinallcases.

The following example illustrates the sizing of vmiter in accordance with this invention. A sizing 4 4 l'ior imtance, in a machine scale operation in which 100% wood from the-wet-strength imparting properties of .aqueous solution containing 455% gelatin and 4 1 product having a wet strength of 10% was obpaper which a-wet strength of 6, unsized. wassized-with an aqueoussolution ofa mixture of gelatin and dimethylol urea instead of one or the other alone. The sizing solution contained 45 4950! gelatine and. 1% of dimethylol urea together with a small amount of aluminum sulfate as the catalyst. The paper was subjected toa operation by passing overwarm rolls. It was found have a wet strength of approximately 50. As pointed out-above the same re-' sult would. be obtained without the catalyst wi alongerd y or heat treatment.

Plperprepared in accordance with my mm.

- tion; due toits high wet strength and blister retreated .in developing. fixing and/or washing baths. Any other product which is subjected to bath composed ,of-4 25 parbof gelatin, 1.1 parts is water or dampness may with advantage bepreof dimethylol urea, 94.85 parts of-water'was'pr pared as follows: The elatin was soaked in asmall proportion of cold ter ii'n'til'it wascor'n pletely swollen. Hot water was then dissolve the 'l-he lol ureathen added in the form'of a-lflbw'al I ter and the remainder or the .Paper was sized by passing 'sh'aet-df-it- I which will liberate;

paredpfrom paper sized in accordance with this -'Iclaim:

.LAmethod ofsizingpaperwhich'comprises ID-treating itwith'gelatinand'a dihydl'olymethyl both in dilute aqueous solution and s ubse quentlysubiecting the paper to a temperature droxymethyl urea without decomposing the cei defromthedlhy jecting the wet paper to a temperature which will liberate formaldehyde from thedihydroxymethyl urea without decomposing the paper.

4. A method of sizing paper which comprises treating it with water containing 2%10% of gelatin, 0.55% of a dihydroxymethyl urea and a small amount of aluminum sulfate all in solution therein and. subsequently subjecting the wet paper to a temperature which will liberate formaldehyde from the dihydroxymethyl urea with-' out decomposing the paper.

5. A method of sizing paper which comprises treating it with water containing 2%-l0% oi gelatin and 0.5-5% of dimethylol urea both in solution therein and subsequently subjecting the wet paper to a temperature which will liberate formaldehyde from the dimethylol urea. without decomposing the paper.

' 6. A method of sizing paper which comprises treating it with water containing approximately l /2% gelatin and 1-3% of dimethylol urea both in solution therein and subsequently subjecting the wet paper to a temperature which will liberate formaldehyde from the dimethylol urea without decomposing the paper.

ROBERT S. BRYCE. 

